The present invention lies in the field of immunodiagnostics.
More particularly, the present invention relates to an antibody, a kit and in vitro methods of diagnosing Alzheimer's disease and/or the predisposition of a subject to develop Alzheimer's disease or cognitive impairment during ageing.
The DNA binding domain (DBD) of human p53 protein (aa 101-306) is characterized by high-grade conformational flexibility and contains one Zn2+ ion coordinated by three cysteines (residues 176, 238 and 242) and one histidine (residue 179). In the wild-type isoform of human p53 protein, the aa 282-297 linear epitope is masked and therefore not available for recognition by an epitope-specific antibody.
However, because of the high-grade flexibility of its DBD domain, p53 protein can assume several conformations, which also characterize its biological activity.
In its wild-type conformation, p53 can bind DNA consensus sequences and transcribe/repress the expression of target genes. In this conformation, the protein exposes an epitope which is recognized by the commercially available, conformationally specific antibody named PAb1620.
There are several grades of conformational alteration states of p53, which correspond to different conformationally altered isoforms. Some mutations in the p53 gene cause a conformational change of the protein, which corresponds to a conformationally altered isoform capable of being recognized by commercially available, conformationally specific antibodies.
Additional conformationally altered isoforms may also derive from post-translational modifications, such as oxidation and/or nitration reactions, which alter the wild-type tertiary structure of the protein.
Buizza L. et al. (“Conformational altered p53 as an early marker of oxidative stress in Alzheimer's disease”, PlosOne 7(1):e29789) and Uberti D et al. (“Identification of a mutant-like conformation of p53 in fibroblasts from sporadic Alzheimer's disease patients”, Neurobiology of Aging 27 (2006) 1193-1201) both identify the expression of mutated p53 protein in patients with Alzheimer's disease, such identification having been made using the anti-p53 antibody PAb240 which binds a cryptic epitope on the amino acid residues 213-217 of p53 protein, not detectable in the wild-type p53 protein.